How to Fight Off the Flu

Most viral infections seep in through your nose and eyes, not your mouth. In fact, in a Journal of Infectious Diseases study, only 8 percent of people fell sick after smooching someone who had a cold. "It's actually safer to kiss someone who's sick than shake his hand," says microbiologist Charles Gerba, Ph.D.

Staying in a Hotel Room: True

A third of hotel room surfaces were still coated in germs nearly a full day after a sick person spent the night, says research from the University of Virginia School of Medicine. Protect yourself by swabbing hard surfaces like doorknobs, light switches, and remote controls with hand sanitizer or alcohol-based wipes.

Using an Old Toothbrush: False

No need to toss your toothbrush after recovering from a cold or flu--you can't reinfect yourself. When you fall ill, your immune system creates antibodies specific to the strain of virus you have. Those good guys stick around to make sure you never get the same exact virus again, says Josh Miller, D.O.

The Sneaky Life of a Virus

Day 1: Someone coughs, spewing viruses all over the grocery-cart handle. You grab the cart and pick up germs along with your dinner.

You rub your nose or eyes, transferring the virus into your sinus system.

Now in your airways, cold or flu viruses begin to reproduce like crazy and block your body's immediate immune response.

Day 2: You feel fine, though virus cells are making their way to your lungs. Also, you're now contagious.

Day 4: You feel hellish.

Many of your symptoms--sneezing, coughing--are side effects of the viral attack on your immune system.

While you can treat those symptoms with meds, drugs won't eradicate a cold or flu. Only time, lots of fluids, and rest will.

Day 5: If you picked up a cold virus, the worst is almost over. You're likely no longer contagious, even if you're still sniffling. If it's the flu, though, you feel as if you've been hit by a truck. You might suffer through a fever, nausea, vomiting, or diarrhea for the next few days as your immune system works like crazy.

Day 10: You could still be contagious for up to a week after your first flu symptoms. Cough or sneeze into a tissue or the crook of your arm -- you won't spread germs via your inner elbow. Better yet, stay home until you're good as new.